This invention relates to non-oxidizable oil-soluble spacing agents useful in fracturing underground oil or gas formations which increases production of oil or gas therefrom.
In the Hydrofrac Process, described in U.S. Pat. No. Re. 23,733 and U.S. Pat. No. 3,217,801, both incorporated herein by reference, a slurry of propping particles containing such materials as walnut shells, glass beads or the like is injected through a well-hole into an oil or gas bearing geologic strata such that the formation is fractured and the particles deposited within the fractured layers. After such treatment, the oil- or gas-bearing strata becomes more porous, allowing a greater percentage recovery of the oil or gas in formation. A problem in this process is encountered after a slurry of only oil-insoluble propping particles is injected. In this situation the particles can agglomerate and effectively plug the fractured cracks in the strata resulting in a formation which is not as porous as it would be if the propping were spaced about the cracks. One solution to this problem is disclosed in U.S. Pat. No. 3,677,941, which is incorporated herein by reference, whereby essentially spherical beads of oil-soluble resin are mixed with the oil-insoluble propping particles. When injected into the formation, the oil-soluble beads will act as spacing agents for the propping particles such that when hydraulic pressure is released and an overburden load reimposed after fracturing and after petroleum is resumed, the spacing agents will be dissolved by the petroleum, leaving the propping particles randomly spaced within the fractured strata. The net result is that oil-bearing strata become more porous and thus the recoverable amount of petroleum within the strata is increased.
As disclosed by prior art, resins suitable for use in spacing agents must be crude-oil soluble and capable of being prilled into deformable, substantially spherical shapes. Further, the prilled resins must be strong enough to remain intact during use and must be sufficiently chemically stable to resist degradation, including oxidation, during manufacture and storage. In order to overcome the degradation problem, the prior art spacing resins, described in U.S. Pat. No. 3,677,941, require an antioxidant.
It is the object of our invention to produce a resin suitable for use as a spacing agent in the Hydrofrac Process which resists degradation without antioxidants. Another object of our invention is to produce deformable spacing agents which have better physical properties than those previously described. Other objects appear hereafter.